Signal translating apparatus



March 12, 1940. GUEDON 2,192,998

SIGNAL TRANSLATING APPARATUS Filed Nov. 50, 1937 I l 69 25 I I r 57 2, n 27 27 1 61 5a 'v ZSnnentor \l\ )XNJI Emile C Guedon 1.9 2.9 .31 2a a? 5 29 Q attorney Patented Mar. 12, 19 40 UNITED STATES SIGNAL TRANSLATING APPARATUS Emile C. Guedon, Audubon, N. J., assignor to Ra dio Corporation of America, a corporation of Delaware Application November 30, 1937, Serial No. 177,293

1'7 Claims.

This invention relates to signal translating apparatus, and more particularly to a pick-up device of the electromagnetic type for use in reproducing sound from phonograph records.

In pick-up devices of the type mentioned, the armature is mounted tovibrate between a pair of associated pole pieces in response to variations in contour of the recorded groove on the record. The armature normally stands midway between the pole pieces in its unexcited condition but is deflected from its central position as the record passes under the needle carried by the armature, thereby generating signal voltages in a winding or coil which surrounds the armature and which is in circuitwith suitable amplifying means and a loudspeaker. In orderto increase the range of operation of the pick-up, it has been proposed to increase the size of the winding about the armature. This, however, also necessitates increasing the length of the armature so that its inertia is increased and its frequency range correspondingly lowered. It has. also been proposed to increase the size of the magnetic structure which supplies the magnetic field in which the active end of the armature operates, but this, too, has a disadvantage in that the magnetic structure cannot be increased too much without making the device too heavy and too cumbersome for proper operation.

The primary object of mypresent invention is to provide an improved electromagnetic pick-i up device having a greater range of operation than those heretofore known and in which the disadvantages noted heretofore are not present.

More particularly, it is an object of my present invention to provide an improved pick-up device of the type set forth which will have a high output regardless of its impedance.

Another object of my invention is to provide an improved pick-up device as aforesaid which has abundant winding space for the armature winding but which does not require a long armature.

Still another object of my invention is to provide an improved electromagnetic pick-up device which may be operated as a low impedance device, an intermediate impedance device, or a very high impedance device, and which can be changed from one to another with great facility.

A further object of my present invention is to provide an improved electromagnetic pick-up in which the air gap can be readily and accurately adjusted to provide the desired flux density.

It is also an object of this invention to provide an improved pick-up device as aforesaid which is very simple in construction and which is highly rounded by a. relatively large high; impedance winding, while the movable armature is surrounded by a relatively small, low impedance winding, and the signal voltages generated by the two coils in response to vibration of the movable rmature may be either used separatelyor combined. Both armatures are terminated in suitable air gaps, and the movable armature is made, short so that it will have a very low moment of inertia about its vibratory axis and therefore will givehigh fidelity reproduction. The magnetic structure is so arranged that the pole pieces for each of the armatures may be readily moved v either toward or away from each other and then fixed in adjusted position whereby the air gaps can be easily'adjusted.

The novel features that I consider characteristic of my invention are set forth with pa-rticu 25 larity in the appended claims. The'invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof will best be understood from the following description of a specific embodiment thereof, when read in connection with the accompanying drawing, in which Figurel is a top plan view of a pick-up device according to my present invention, with the cover removed,

Figure 2 is a sectional view thereof taken on the line 22 of Fig. 1,

Figure 3 is a sectional view taken on the line 33 of Fig. 2, and

Figure 4 is a wiring diagram showing how the 40 two windings of the pick-up device may be connected.

Referring more particularly to the drawing, wherein similar reference numerals designate corresponding parts throughout, there is shown a die cast supporting member i of non-magnetic material provided with a bushing 3 by means of which the device may be mounted on a suitable supporting arm (not shown) and having also a forwardly extending plate member 5 terminating in a needle guide I having an opening or slot 9 through which a needle may be, inserted for a purpose presently to be described. Secured to the plate 5 by the screws .II are a pair of oppositely directed blocks l3 of magnetic material ,55 I

to which a permanent magnet i5 is spot welded or otherwise suitably secured, the blocks l3 supporting at their tops a pair of cooperating pole pieces El and at their bottoms another pair of cooperating pole pieces id. The pole pieces I! lie in the same plane and are physically separated from each other to provide an air gap 2| therebetween, while the pole pieces 19, also both lying in a, single plane, are physically separated from each other to provide'an air gap 23 therebetween. Each of the pole pieces is provided with a transverse slot 25 in which is received the flat head of a screw 21, each in turn threadedlyreceived in the blocks it for axial movement in a plane parallel to the planes of the two sets of pole pieces. ,It will be obvious that adjustment of the screws ii in their threaded openings will cause the pole pieces of the respective pairs to move either toward or away from each other whereby to vary the size of the air gaps 2i and 23. Each of the pole pieces il and i8 is also provided with an opening 29 through which extends a locking screw 3i threaded in the blocks I13 and serving to lock the respective pole pieces in any position of adjustment as determined by the screws 21. The openings 29 are made longer than the diameters of the screws 3! to permit a substantial degree of adjustment of the several pole pieces longitudinally.

It will be noted that the pole pieces I? are located to one side ofthe plate 5 and the pole pieces it are located on the other side of the plate 5. Fixed to the plate 5, substantially centrally thereof, is a stationary'armature 33 having the major portion thereof extending above the plate 5 and terminating in the air gap 2!. The armature 33 also extends a short distance below the plate 5 and pivotally carries an armature shaft 35 on which is formed a downwardly extending, short armature 3'! the active end of which terminates in the airgap 23. A spring 39, formed of piano wire or the like and suitably secured to the blocks it, as by a pair of clamps it, and to the armature shaft 35, tends constan ly to maintain the armature 3i centered in the air gap 23. The armature shaft 35 may be further supported in a bearing fill carried by the needle guide '1' and. is provided with a needle socket $3 in which a needle (not shown) may be secured by a screw 45. The other end of the armature shaft 35 may be embedded within a suitable clamping member l! secured to the frame member i, as by a screw 419. The damping member it may be of the type disclosed in the Kendall 'Patent No. 2,092,884.

Within the space between the plate 5 and the pole pieces I1, and surrounding the major portion of the stationary armature 33, is a winding or coil 5i having a high impedance, In the space between the plate 5 and the lower pole pieces i9, and surrounding the armature 3?, is a small winding or coil 53 having a low impedance. The coil 53 may be supported in place by a fibrous or other similar plate 55 to which it is cemented and which, in turn, is carried by the studs 51 on the plate 5. The coils 5i and 53 are preferably serially connected, as shown in Fig, i, with their free ends or leads 59 and ti, respectively, connected to the terminals 63 and 65 on a terminal block 61 from which connection may be made to an external amplifying circuit. The

Y circuit comprising the windings 5i and 53 is also provided with a. lead 69 at the junction point ll of the two coils; the lead 69 being connected to a terminal 13 on the terminal block 6?.

It will be obvious, therefore, that by connecting an external amplifying circuit to the terminals 63 and T3, the output of the high impedance coil 5! may be employed; by connecting an external amplifying circuit to the terminals 65 and 13,

the output from the low impedance coil 53 may be utilized; and by connecting the external amplifying circuit to the terminals 63 and 65, a very high impedance pick-up is provided and the combined output from both coils may be utilized. Inasmuch as the armature 31 is very short and light and has a low moment of inertia about its vibratory axis 35, it will be effective toreproduce high frequency sounds with great fidelity. At the same time, by reason of the greatly enlarged winding space, use may be made of both windings to reproduce the lower frequencies with great fidelity. Thus a pick-up device constructed according to my present invention will reproduce very efficiently sounds covering a very wide range of-the audio spectrum. 1

- As noted heretofore, the device may be mounted on a suitable suspension arm and the terminals 63, 65 and/or 73 may be fitted to suitable corresponding terminals on the suspension arm.

to operate either as a low impedance pick-up, a very high impedance pick-up, or a pick-up of intermediate impedance. The slot9 in the needle guide I is aligned with the needle socket 43 to permit easily inserting 'a needle in the socket from the top, it being merely necessary to insert the needle into the slot 9 and permit it to drop through the socket 43 onto an indexingdevice of the type described in my copending application Serial No. 187,935, filed Jan. 31, 1938, after which the screw 45 is tightened against the needle. I I

Although I have shown and described but a single embodiment of my invention, it will be apparent to those skilled in the art that many modifications thereof and changes therein are possible. I'therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appendedclaims. f i I claim as my invention:

1. In'an electrical signal translating device, the combination of a supporting member, a stationary armature carried by said supporting member, and a vibratory armature pivotally car-.

. ried by said stationary armature.

2. In an electrical signal translating device, the combination of a supporting'member, a'relatively long stationary armature carried by said supporting member, and a relatively short vibratory armature pivotally carried by said stationary armature, said short armature having a low moment of inertia about its vibratory axis.

3. In an electrical signal translating device, the combination of asupporting member, a stationary armature carried by said supporting member a vibratory armature pivotally carried by said stationary armature, and separate voltage generating means associated with eachof said armatures. v 1

4. In an electrical signal translating device, the combination of a supporting member, a stationary armature carried by said supporting member, a vibratory armature pivotally carried by said stationary armature, a winding of relatively high impedance associated with said stationary armature, and a windingof relatively low impedance associated with said vibratory armature.

5. The invention set forth in claim'characterized in that said windings are connected in series and characterized further in that the circuit comprising said windings includes a lead connected to the junction pointof said windings whereby the outputs of either of said windings or the combined outputs of both of said windings may be utilized.

6. In an electrical signal translating device, the combination of a supporting member, a stationary armature carried by said supporting member, a vibratory armature pivotally carried by said stationary armature, and magnetic structure providing two separate pairs of pole pieces, each pair of pole pieces having an air gap therebetween, said stationary armature terminating in one of said air gaps and said vibratory armature having its active end in the other of said air gaps.

'7. In an electrical signal translating device, the combination of a supporting member, a stationary armature carried by said supporting member, a vibratory armature pivotally carried by said stationary armature, a magnetic structure providing two separate pairs of pole pieces, each pair of pole pieces having an air gap therebetween, said stationary armature terminating in one of said air gaps and said vibratory armature having its active end in the other of said air gaps, and means constantly tending to hold saidvibratory armature centered in its air gap.

8. The invention set forth in claim 6 characterized by the addition of means for individually adjusting the pole pieces of each pair relative to one another whereby said air gaps may be varied.

9. The invention set forth in claim 6 characterized in that one pair of pole pieces is located on one side of said supporting member and the other pair of pole pieces is located on the other side of said supporting member, and characterized furtherin that said stationary armature extends through said supporting member but has its major portion extending on said first named side, and said vibratory armature is located on said second named side.

10. In an electrical signal translating device, the combination of a supporting member, a stationary armature carried by' said supporting member and extending therethrough with its major portion lying on one side of said supporting member, a vibratory armature pivotally carried by said stationary armature on the other side of said supporting member, and magnetic structure providing two separate pairs of pole pieces, one of said pairs of pole pieces lying on the first named side of said supporting member and the other lying on the second named side of said supporting member and each pair of pole pieces having an air gap therebetween, said stationary armature terminating in the air gap between said first named pair of pole pieces and said vibratory armature having its active end in the air gap between said other pair of pole pieces.

11. In an electrical signal translating device,

the combination of asupporting member, a stationary armature carried by said supporting member and extending therethrough with its other lying on the second named side of said supporting member and each pair of pole pieces having an air gap therebetween, said stationary armature terminating in the air gap between said first named pair of pole pieces and said vibratory armature having its active end in the air gap between said other pair Of pole pieces, aielatively high impedance winding surrounding said stationary armature and located in the space between said supporting member and said first named pair of pole pieces, and a relatively low impedance winding surrounding said vibratory armature and located in the space between said supporting member and said other pair of pole pieces.

12. The invention set forth in claim 11 characterized in that said windings are serially connected andcharacterized further in that the circuit comprising said windings is provided with a lead at the junction point of said windings whereby the outputs of either of said windings or their combined outputs may be utilized.

13. In an electromagnetic signal translating device, the. combination of means providing a source of magnetic flux, a pair of pole pieces having transversely extending slots therein carried by said means, said pole pieces lying in a common plane and being physically separated from each other to provide an air gap therebetween, and a pair of screws mounted on said fiuxproviding means formovement axially in a plane parallel to that of said pole pieces and having heads thereon received within the slots in said pole pieces,

said screws being so arranged on said flux providing means that movement thereof axially will cause said pole pieces to move either toward or away from each other in their own plane whereby to vary the size of said air gap.

14. The invention set forth in claim 1 characterized in that said supporting member is formed of non-magnetic material, and characterized further in that said armatures are both formed of magnetic material.

15. In an electrical signal'translating device, the combination of meansproviding a magnetic circuit and. including two air gaps, a stationary armature having a portion located in one of said air gaps, and a movable armature associated with said stationary armature, said movable armature having a portion located in the other of said air gaps. I

16. In anelectrical signal translating device, the combination of means providing a magnetic circuit and including two air gaps, a stationary armature having a portion located in one of said air gaps, and a movable armature associated with said stationary armature, said movable armature having a relatively small moment of inertia and having a portion located in the other of said air gaps.

17. In an electrical signal translating device, the combination of means providing a magnetic circuit and including two air gaps, a stationary armature having a portion located in one of said air gaps, a high impedance winding surrounding said stationary armature, a movable armature associated with said stationary armature, said movable armature havinga portion located in the other of said air gaps, and a low impedance winding surrounding said movable armature.

' EMILE C. GUEDON. 

